Great hook or connection to the real world for math and current research. Also interesting for enrichment material about exponential equations or prime numbers.
"So according to our "big tent" model of PBL, some of the newer "X-BLs" -- problem-, challenge- and design-based -- are basically modern versions of the same concept. They feature, to varying degrees, all of BIE's 8 Essential Elements of PBL, although each has its own distinct flavor. (And by the way, each of these three, along with project-based learning, falls under the general category of inquiry-based learning -- which also includes research papers, scientific investigations, Socratic Seminars or other text-based discussions, etc."